Solar Terrestrial Activity Report

Last major update issued on May 24, 2012 at 05:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 19, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to minor storm on May 23. Solar wind speed at SOHO ranged between 440 and 723 km/s under the influence of a high speed stream from CH517.

Solar flux measured at 20h UTC on 2.8 GHz was 117.2 (decreasing 2.0 over the last solar rotation). The Potsdam WDC planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.4). Three hour interval K indices: 45532223 (planetary), 44432232 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11482 [N15W87] decayed slowly as it rotated to the northwest limb.
Region 11483 [S23W81] was quiet and stable.
Region 11484 [N12W54] decayed slowly and was mostly quiet.
Region 11486 [N16E01] was quiet and stable.
Region 11488 [N11E40] was quiet and stable.

Spotted active regions not numbered by NOAA/SWPC:
S1659 [N14W24] was quiet and stable.
S1671 [S18E25] was quiet and stable.
New region S1675 [S13E73] emerged near the east limb with several spots.
New region S1676 [S10E34] emerged with tiny spots.
New region S1677 [N06E10] emerged with a tiny spot.
New region S1678 [N22W03] emerged to the northwest of AR 11486 and is developing slowly.
New region S1679 [N12W05] emerged woth a tiny spot.

Coronal mass ejections (CMEs)

May 21-23: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH517) was in an Earth facing position on May 19-20. A coronal hole (CH518) in the northern hemisphere was in an Earth facing position on May 21 but may have been too far to the north to become geoeffective. A poorly defined southern hemisphere coronal hole (CH519) will be Earth facing on May 23-24.

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 24 due to effects from CH517. Effects from CH518 could cause some unsettled intervals on May 24-25 while CH519 could cause quiet to unsettled conditions on May 26-28.

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region	Date numbered detected	Spot count			Location at midnight	Area	Classification		SDO / HMI 4K continuum image with magnetic polarity overlay		Comment
		SWPC	STAR SDO				SWPC	STAR	Current	Previous
			2K	1K
11482	2012.05.11 2012.05.13	3	1	1	N15W84	0190	CSO	HSX			location: N15W87
11483	2012.05.12 2012.05.13	3	4	3	S24W79	0030	CRO	CRO
11481	2012.05.12 2012.05.13				S10W78						plage location: S10W55
11484	2012.05.13	13	21	10	N11W56	0240	EAI	DAI			location: N12W54
S1654	2012.05.14				S25W50						plage
S1659	2012.05.15		3		N14W23	0000		BXO
11485	2012.05.15				S20W43						plage location: S18W41
11486	2012.05.17 2012.05.18	6	5	1	N16E02	0180	CSO	CSO
S1663	2012.05.17				N12W32						plage
11487	2012.05.18 2012.05.20				N18W47						plage location: N20W43
S1666	2012.05.18				S19W30						plage
S1667	2012.05.19				N04E03						plage
S1668	2012.05.20				N13W45						plage
11489	2012.05.21 2012.05.22	1			S30E40	0000		AXX			spotless formerly AR S1670
S1671	2012.05.21		6	4	S18E25	0010		BXO
11488	2012.05.21 2012.05.22	5	15	8	N11E41	0010	BXO	BXO
S1673	2012.05.21				N27W42						plage
S1674	2012.05.22				S21E41						plage
S1675	2012.05.23		5	1	S13E73	0010		BXO
S1676	2012.05.23		2		S10E34	0000		AXX
S1677	2012.05.23		1		N06E10	0000		AXX
S1678	2012.05.23		5	3	N22W03	0010		BXO
S1679	2012.05.23		1		N12W05	0000		AXX
Total spot count:		31	69	31
Sunspot number:		91	189	111	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		49	87	49	(Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number):		55	66	61	k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.